Demographic Perspectives on Human Senescence

Demographic approaches to modeling and forecasting mortality are often based on the observation of short-term trends in death statistics and the assumption that future mortality will exhibit patterns similar to those of the recent past. This extrapolation method has led some demographers to conclude that life expectancy in the not too remote future will reach 100 years. Similar predictions follow from another demographic model that establishes a hypothetical link between risk factor modification and changes in death rates. These predictions are examined within the context of the observed mortality record of the United States and their biological plausibility is assessed in light of evolutionary theories of senescence. Results indicate that these demographic models lead to mortality schedules that do not follow from the observed mortality record and that are inconsistent with predictions of biologically based limits to longevity. Although there is probably not a genetic program for death the biology of our species places inherent limits on human longevity. (SUMMARY IN FRE AND SPA) (EXCERPT)